Alkaline-developing photoresists are used for patterning, for example, chemical-milling and the production of printed wiring boards. As foaming during production is detrimental to the production of printed wiring boards, measures have conventionally been taken to suppress foaming through the addition of antifoaming agents. The ingredients of certain antifoaming agents, such as polyoxyalkylene ethers, glycerol monostearate, polyoxyethylene sorbitan monostearate, and coconut alcohol, are themselves contaminants in developers and the products of these printed wiring boards.
On the other hand, some ingredients of photoresists, such as polymers having a structure unit of styrenes, methyl methacrylate, ethyl acrylate, and methacrylic acid, are separated and deposited on the wall of conduits. The deposits are also contaminants in developers and the products. In order to remove the separated materials described above, 3% aqueous hydrochloric-acid solution and commercial cleaning solution; some cleaning solution containing caustic soda, sodium acetate, butyldiglycol, or surfactants; and those including hydrochloric acid or hydroxycarboxylic acid, as have conventionally been used. However, these methods involve the high costs of chemical cleansing and waste treatment, and are may not be sufficiently effective, depending on the photoresist ingredients.
In this technological environment, a magnetic water-treatment apparatus is publicly known. As the apparatus separates the association of clustered water molecules in order to reactivate them, it may also be utilized to perform defoaming in the development step described above if it functions as expected. However, as the fluid to be treated is exposed to magnetic flux generated between a pair of magnets positioned on opposite ends of a flow of water in the case of the water-treatment apparatus described above, the pair of magnets must be positioned so as to face each other. Therefore, a strong magnetic field also exists in regions other than the area under examination, resulting in the problems of a low efficiency in magnetic-field utilization and a significant loss in magnetic force. In addition, utilization of a water-treatment apparatus such as that described above, comprising a uniform magnetic field only, cannot be expected to have a significant effect.
U.S. Pat. No. 5,074,998 is an exemplary invention intended to prevent the deposition of scale inside conduits. The invention has a constitution in which solenoid-type electric coils are positioned alongside and outside or inside the conduit, a magnetic field, generated by charging the electric coils, is applied to the fluid in the conduit. Control of the strength of this magnetic field is also described in the invention. This is done by adjusting the amplifying-signal electric current of the coil to the characteristic frequency of the scale-forming substance. The fluid is exposed to a magnetic field only once while it flows through a conduit utilizing an apparatus of the invention described above.